The present invention relates to computer animation. More specifically, the present invention relates to techniques for rendering finely-detail surfaces, such as cloth.
In computer animation, a user, known as an animator, typically specifies poses for models of an object on a computer system. Based upon the specified poses with respect to time, the object may appear to be animated in a series of rendered images. To facilitate posing models of objects in a computer animation environment, the assignee of the present patent application, ImageMovers Digital has pioneered the use of physical motion capture techniques using live actors. By way of example, ImageMovers has used a combination of motion capture techniques and traditional computer animation techniques to produce feature-length films including: “The Polar Express” (2004), “Monster House” (2006), “Beowulf” (2007), which have garnered several Academy Award nominations.
In the process of rendering the above full-length computer animation/computer generated imagery, the inventor of the present invention discovered that it was very challenging to render highly detailed surfaces of objects. One method for rendering such surfaces was to perform highly-detailed surface simulations and analyses to determine the surface appearance of an object for every image. These computations would be based upon a detailed physical description of the surface (e.g. cloth).
A problem, determined by the inventor with this approach, was that such highly-detailed surface simulations were very computationally intensive, and sometimes took days to calculate. Accordingly, it was impractical to render a surface of an object that appeared in many different scenes based upon surface simulations, as part of a rendering pipeline.
Another drawback, contemplated by the inventor, was that because the conditions of the surface of an object were quite variable from scene to scene, it required different surface simulations to be run for each of the different conditions of the object surface (e.g. clothes moving). Such a solution was not practical.
As still another drawback, considered by the inventor, was that when performing multiple surface simulations, the different computed surfaces sometimes lacked continuity. More specifically, when the surface simulations were performed, characteristic object surface details computed in a first image may be completely different from characteristic object surface details computed in a second image. As a result, the differences in object surface details between the first image and second image would manifest itself to the user as distracting surface flickers.
In light of the above, what is desired are solutions to the above problems, without the drawbacks described, above.